Outside of Shrouded Bunker in the wasteland an RC Car is deployed when you pass. Park your vehicle on the slope opposite, under the bridge, then get behind the RC Car where it is deployed. Shoot the RC Car and pick up the salvage - repeat as required.
Once at Subway Town, you are able to purchase repeating deals from Stew, behind the shop.
Some of the items you can buy can be sold straight away at Jani's Supplies for a higher price. You can, for example, buy Viper Rockets for $66 which can then be sold to Jani for $75. This can be repeated to your heart's content!